Transfer sheets and method of making the same



May 30, 1961 w. RITZERFELD ETAL 2,986,473

TRANSFER SHEETS AND METHOD OF MAKING THE SAME Filed March 11, 1958 s Sheets-Sheet 1 y 1961 w.. RITZERFELD EIAL 2,986,473

TRANSFER SHEETS AND METHOD OF MAKING THE SAME Filed March 11, 1958 3 Sheets-Sheet 2 May 30, 1961 w RITZERFELD EI'AL 2,986,473

TRANSFER SHEETS AND METHOD OF MAKING THE SAME Filed March 11, 1958 5 Sheets-Sheet 3 United States TRANSFER SHEETS AND METHOD OF MAKING THE SAME Wilhelm Ritzerfeld, 14 Schorlemer Allee, Berlin-Dahlem, Germany, and Gerhard Ritzerfeld, 21 Franzensbader Str., Berlin-Grunewald, Germany The present invention relates to a transfer sheet and to a method of making the same and, more particularly, the present invention relates to a transfer sheet capable of transferring its fatty layer onto the image transferring portions of a lithographic printing foil.

Transfer sheets of the kind to which the present invention relates are preferably placed with their fatty face in contact with the working face of an ofiset printing foil and a portion of the fatty layer of the autographic transfer sheet is transferred to the working face of the printing foil by application of pressure. The configuration on the printing foil of the transferred portion of the fatty layer corresponds to the printing image. Upon application of printing ink, the portions of the printing foil thus covered with fat or the like, will retain printing ink while the simultaneously moistened fat-free portions of the working face of the printing foil will remain free of printing ink so that the ink will be transferred from the fatty portions of the printing foil only onto the paper or the like to be imprinted.

It is therefore of the greatest importance that the transfer of portions of the fatty layer of the autographic transfer sheet onto the printing foil corresponds exactly to the configuration of the printing image. Therefore it is desired that only considerable pressure such as is exerted by a typewriter key or can be exerted by a ballpoint pen or pencil, will cause transfer of fatty material from the transfer sheet to the working face of the printing foil. On the other hand, it is essential that lesser pressure such as might be exerted by holding a transfer sheet and printing foil together by hand or by inserting the same in a typewriter will not cause transfer of fatty material.

It is therefore an object of the present invention to provide a transfer sheet and a method of making the same which will be capable of transferring fatty material to a printing foil only upon exertion of a predetermined relatively considerable minimum pressure.

It is another object of the present invention to provide a method whereby such transfer sheet can be produced in a simple and economical manner.

Other objects and advantages of the present invention will become apparent by a further reading of a description and the appended claims.

With the above and other objects in view, the present invention mainly comprises in a method of producing a transfer sheet, the steps of forming on one face of a backing sheet a layer of a fatty substance being solid at room temperature and being adapted to be liquified upon being heated to a predetermined elevated temperature, applying to the free face of the fatty layer a finely divided material which is insoluble in the fatty substance, so as to substantially cover the free face of the fatty layer, heating the fatty layer at the predetermined temperature for a period of time sufiicient to melt at least that portion thereof which is farthest distant from the backing sheet, thereby partially embedding the material in the portion of the fatty layer, the steps of applying the material and of heating the fatty layer being carried out in atent any desired sequence, and allowing the thus-formed composite sheet to cool so as to solidify the fatty layer, whereby a thin, substantially fat-free, porous, protective covering is formed on the free face of the fatty layer.

The present invention also includes a transfer sheet, comprising, in combination, a backing sheet, a solid layer of fatty material covering one face of the autographic transfer sheet, and a finely divided, solid, fat-insoluble material partially embedded in and extending outwardly of the outer portion of the fatty layer so as to substantially cover the same and forming a porous protective covering thereon.

In a preferred manner, the present invention may be carried out by forming on one face of a backing sheet a layer of a fatty substance having a metal powder distributed therethrough and being solid at room temperature and being adapted to be liquefied upon being heated to a predetermined elevated temperature, heating the fatty layer at the predetermined temperature for a period of time sufiicient to melt at least that portion thereof, which is farthest distant from the backing sheet, subjecting the fatty layer to an electric charge, applying by electrostatic deposition to the molten free face of the fatty layer a finely divided electrically charged solid material of opposite polarity which is insoluble in the fatty substance, so as to substantially cover the free face of the fatty layer and partially embedding the material in the molten portion of the fatty layer, and allowing the thus-formed composite sheet to cool so as to solidify the fatty layer, thereby firmly adhering the material to the outer portion of the fatty layer, whereby a thin, substantially fat-free, porous, protective covering is formed on the free face of the fatty layer.

Thus, according to the present invention, a liquid composition or mixture of fats and waxes or wax-like synthetic materials is applied in hot condition onto a paper band or the like and a fat-free pulverulent or liquid material is subsequently applied to or sprayed onto the free face of the thus formed fatty layer. The fatty layer which is solid at room temperature is heated to its melting temperature, either prior, during or after application of the non-fatty material so that upon subsequent cooling, the non-fatty material will be firmly adhered to the solidified surface portion of the fatty material and will form on the same a non-fatty porous layer. This layer has the particular characteristic of giving to the surface of the transfer sheet, according to the present invention, a slightly roughened structure which prevents transfer of any portion of the fatty layer to the printing foil under slight pressure. Only upon considerable pressure exerted for instance by a typewriter key or by means of a pencil or ballpoint pen, the wax and fatty layer will come in contact with and will be transferred to the printing foil, since upon exertion of such considerable pressure, the usually granulated non-fatty surface layer will sink into the fatty layer, below the surface thereof so that direct contact between the printing foil and the fatty material is established. In this manner, the difficulties of prior art transfer sheets which permitted inadverted transfer of fatty material upon slight pressure and consequent smudging of the printing foil, are overcome.

As the non-fatty pulverulent solid material for forming the protective surface layer covering the fatty material, non-hygroscopic rnineralic materials, such as calcium carbonate, barium sulphate, talcum, kaolin, kieselguhr, slatemeal or pumice powder have been advantageously used according to the present invention. However, the covering material may also be applied in liquid form, i.e. either dissolved in a suitable solvent or as a suspension. For instance lacquers, such as zapon varnish or shellac, dissolved in suitable volatile organic solvents have been successfully applied to the fatty layer of a transfer sheet,

3.. Polyvinyl acetate may be mentioned as an example of a material which may be applied to the surface of the fatty layer in the form of an aqueous dispersion.

Application of the solid pulverulent materials to the surface of the fatty layer may be carried out ina great variety of ways. The covering material may be dusted onto-the molten layer, for instance, by spraying through nozzles by means of pressurized air, or solid material may be electrostatically applied to the molten layer, however, application of the material may also be carried out onto the solidified fatty layer which then subsequently has to'be heated so as to be transformed into a viscous condition. It is also possible to combine both of these alternatives by heating the fatty layer shortly prior to application of the covering material and again after spraying of the covering material thereon. For electrostatic application of a pulverulent material it is sometimes advantageous to adrnix to the fatty layer a metal powder in order to make it possible to electrically charge the fatty layer itself.

It has been found advantageous and is to be considered also within the scope of the present invention to include in the fatty layer not only fatty substances and waxes or wax-like synthetic compounds, but also including therein non-coloring pigments such as white pigments. Thereby it is achieved that by application of a sutficiently strong pressure a greater proportion of the fatty layer, in fact nearly the entire thickness of the fatty layer is transferred from the autographic transfer sheet to the covering face of the printing foil. Thereby, of course, only such pigments are to be used which will not cause contamination of the printing ink eventually applied to the working face of the printing foil and which will also not be capable of causing soiling of hands or clothing. Such pigments can be introduced, according to the present invention, within a wide quantitative range. Generally it has been found advantageous to use pigments in a quantity corresponding to between -70% of the total weight of the fatty layer, and preferably in a quantity of between -35%. Pigments suitable for incorporation into the fatty layer include lithopone and barium sulphate.

The following examples will serve to illustrate preferred compositions of the fatty layer according to the present invention.

Example 1 G. Wool fat 1500 Castor oil 2000 Montan wax 4000 Barite 7000 Example 2 G. Albertol (phenolfonnaldehyde-resin) 3000 Castor oil 1400 Montan wax 4000 Lithopone 8500 In the above examples montan wax may be partly or completely replaced by a polyethylene wax.

It should be noted that all examples in the present case are given as illustrative only, the present invention, however, not being limited by the specific details of the examples.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its constructionand its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Figs. 1, 3 and 4 are schematic illustrations of devices for carrying out the method of the present invention; and- Fig. 2 is an elevational cross sectional view of a transfer sheet according to the present invention, also illustrating the use of the same.

Referring now to the drawings, and particularly to Fig. l, a paper storage roll 1 is shown from which a paper web 2 passes over transporting rollers 3, 4, 5 and 6 and is positioned by guide rollers 7 and 8 against application roller 9. Application roller 9 is partly immersed in container 10 containing a liquid fatty substance and serves for applying the liquid fatty substance onto paper web 2. Scraper l1 removes any excess of fatty substance from the paper web. Subsequent rollers i2, 13 and 14 as Well as rollers 8 and 9 are heated as indicated by the letter H, in order to guarantee even distribution of the fatty or wax-like layer on the paper web. After passing roller 14, the paper web passes underneath sprayer 15 through which the finely divided material 17 is sprayed onto paper web 2 by means of a pump 16 communicating with storage container 18. Thereafter the thus formed composite sheet passes over cold guide roller 19 insuring complete solidification of the layer of fatty material, and the thus completed product is rolled up to form storage roll 20.

Fig. 3 shows a somewhat similar arrangement as illustrated in Fig. 1, however, an additional heating roller 26 is provided and transport roller 27 is not heated but retained in cold condition. The sprayed material 17 is thus applied to a cold fatty layer and subsequently, by passing heated roller 26 which causes at least softening and partial melting of the fatty layer, firmly adheres to the same.

Fig. 4 illustrates a device whereby the covering material is applied by electrical means. Paper web 28 passes over heated rollers 29 and 30 and thereafter on top of metal plate 31 which is charged with a negative potential so that paper web 28 will also carry a negative potential. The source of the negative potential is rectifier 32 which obtains electric current from a source 34 of alternating current via transformer 33. The positive tap of rectifier 32 connects via vibrator convertor 35 with grids 36. On top of grids 36 storage container 37 is arranged with a grating device 38 which serves for even distribution of the pulverulent material 39 passing from storage container 38 through grids 36 onto the fatty layer of the paper web 28. The dust-like particles passing through grid 36 are positively charged and consequently attracted by negatively charged paper web 28. Paper web 28 then passes underneath positively charged collector troughs 40. While passing underneath troughs 40, all dust-like particles 41 which do not firmly adhere to the fatty layer and which are now negatively charged will be attracted by the positively charged collecting troughs 40 and deposited onto the same. The web then passes over roller 19 and is rolled into a storage roll as described in connection with Figs. 1 and 3.

Referring now to Fig. 2, the transfer sheet is shown to consist of carrier sheet 25, fatty or wax layer 23 and particulate covering 24 on the free surface of fatty layer 23. The transfer sheet is shown positioned against a printing foil 22. Transfer of the fatty layer from the transfer sheet to printing foil 22 will now be accomplished when typewriter key 21 hits printing foil 22 thus exerting sufiicient pressure onto the transfer sheet to embed the particles 24 completely in the fatty layer and thereby to establish intimate contact between the fatty layer 23 and printing foil 22.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of transfer sheets differing from the types described above.

While the invention has been illustrated and described as embodied in a transfer sheet for transferring fatty material to an offset printing foil, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a method of producing a transfer sheet, the steps of forming on one face of a backing sheet a solid layer of a fatty substance being solid at room temperature and being adapted to be liquefied upon being heated to a predetermined elevated temperature; heating said fatty layer at said predetermined temperature for a period of time sufficient to melt at least that portion thereof which is farthest distant from said backing sheet; dusting onto the molten free face of said fatty layer a covering layer consisting of finely divided granulated pulverulent solid material which is insoluble in said fatty substance, said steps of heating said fatty layer and of applying said pulverulent material being carried out in such a manner as to partially embed individual particles of said material in said fatty layer leaving portions of said individual particles exposed and extending outwardly of the free face of said fatty layer; and allowing the thus-formed composite sheet to cool so as to solidify said fatty layer, thereby firmly adhering said partially embedded finely divided solid material to the outer portion of said fatty layer thus forming a transfer sheet having a protective, rough outer portion formed of the outwardly extending free portions of said partially embedded particles.

2. In a method of producing a transfer sheet, the steps of forming on one face of a backing sheet a layer of a fatty substance being solid at room temperature and being adapted to be liquefied upon being heated to a predetermined elevated temperature; dusting onto the free face of said fatty layer a covering layer consisting of a finely divided granulated pulverulent solid material which is insoluble in said fatty substance; heating said fatty layer with said covering layer thereon to at least said predetermined temperature for a period of time sufficient to melt at least that portion thereof which is farthest distant from said backing sheet, so as to partially embed individual particles of said material in said portion of said fatty layer leaving portions of said individual particles exposed and extending outwardly of the free face of said fatty layer; and allowing the thus-formed composite sheet to cool so as to solidify said fatty layer and to firmly adhere the partially embedded portion of said material to the outer portion of said fatty layer, thus forming a transfer sheet having a protective, rough outer portion formed of the outwardly extending free portions of said partially embedded particles.

3. In a method of producing a transfer sheet, the steps of forming on one face of a backing sheet a layer of a fatty substance being solid at room temperature and being adapted to be liquefied upon being heated to a predetermined elevated temperature; dusting onto the free face of said fatty layer a finely divided granulated pulverulent solid material selected from the group consisting of calcium carbonate, barium sulphate, talcum, kaolin, kieselguhr, slate-meal and pumice powder so as to form on said layer of a fatty substance a covering layer consisting of said pulverulent solid material; heating said fatty layer to at least said predetermined temperature for a period of time sufiicient to melt at least that portion thereof which is farthest distant from said backing sheet, so as to partially embed individual particles of said material in said fatty layer leaving portions of said individual particles exposed and extending outwardly of said free face of said fatty layer allowing the thus-formed composite sheet to cool so as to solidify said fatty layer thereby firmly adhering said partially embedded pulverulent material thereto and removing from the surface of said composite sheet any free non-adhering particles of said material, thereby forming a transfer sheet having a protective, rough outer portion formed of the outwardly extending free portions of said partially embedded particles.

4. In a method of producing a transfer sheet, the steps of forming on one face of a backing sheet a layer of a fatty substance having a non-coloring pigment distributed therethrough, being solid at room temperature and being adapted to be liquefied upon being heated to a predetermined elevated temperature; heating said fatty layer at said predetermined temperature for a period of time sufficient to melt at least that portion thereof which is farthest distant from said backing sheet; spraying onto said molten portion of said fatty layer a finely divided granulated pulverulent non-hygroscopic mineralic material insoluble in said fatty substance so as to partially embed individual particles of said material in said fatty layer leaving portions of said individual particles exposed and extending outwardly of said free face of said fatty layer; and allowing the thus-formed composite sheet to cool so as to solidify said fatty layer, thereby forming a transfer sheet having a protective, rough outer portion formed of the outwardly extending free portions of said partially embedded particles.

5. A transfer sheet, comprising, in combination, a backing sheet; a solid layer of fatty material covering one face of said backing sheet; and a covering layer of particles of a finely divided granulated pulverulent, solid substance insoluble in said fatty material, substantially all of said particles, respectively, being partially embedded in said fatty layer and having exposed portions extending outwardly of said outer portion of said fatty layer, whereby a transfer sheet is formed having a rough protective outer portion formed of said outwardly extending free portions of said partially embedded particles, thus permitting transfer of portions of said fatty layer onto a surface contacting said protective portion only upon subjecting said free portions of said particles to a predetermined degree of pressure sufiicient to cause sinking of said entire particles below the surface of said fatty layer.

6. A transfer sheet, comprising, in combination, a backing sheet; a solid layer of fatty material having distributed therethrough a non-coloring pigment, covering one face of said backing sheet; and a covering layer of particles of a finely divided, granulated, pulverulent solid substance insoluble in said fatty material, substantially all of said particles, respectively, being partially embedded in said fatty layer and having exposed portions extending outwardly of said outer portion of said fatty layer, whereby a transfer sheet is formed having a rough protective outer portion formed of said outwardly extending free portions of said partially embedded particles, thus permitting transfer of portions of said fatty layer onto a surface contacting said protective portion only upon subjecting said free portions of said particles to a predetermined degree of pressure sufiicient to cause sinking of said entire particles below the surface of said fatty layer.

7. A transfer sheet, comprising, in combination, a backing sheet; a solid layer of fatty material consisting essentially of at least one substance selected from the group consisting of solid fats, natural and synthetic waxes, and having distributed therethrough a non-coloring pigment, covering one face of said backing sheet; and a covering layer of particles of a finely divided, granu lated, pulverulent, solid substance insoluble in said fatty material, substantially all of said particles, respectively, being partially embedded in said fatty layer and having exposed portions extending outwardly of said outer portion of said fatty layer, whereby a transfer sheet is formed having a rough protective outer portion formed of said outwardly extending free portions of said partially embedded particles, thus permitting transfer of portions of said fatty layer onto a surface contacting said protective portion only upon subjecting said free portions of saidparticles to a predetermined degree of pressure suflicient to cause sinking of said entire particles below the surface of said fatty layer.

8. A transfer sheet, comprising, in combination, a backing sheet; a solid layer of fatty material having distributed therethrough in a quantity equal to between 10 and 70% of the weight of said solid layer, a pigment selected from the group consisting of lithopone and barium sulfate, covering one face of said autographic backing sheet; and a layer of particles of a finely divided, granulated, pulverulent, solid substance insoluble in said fatty material, substantially all of said particles, respectively, being partially embedded in said fatty layer and having exposed portions extending outwardly of said outer portion of said fatty layer, whereby a transfer sheet is formed having a rough protective outer portion formed of said outwardly extending free portions of said partially embedded particles, thus permitting transfer of portions of said fatty layer onto a surface contacting said 8 protective portion only upon subjecting said free portions of said particles to a predetermined degree of pressure suflicient to cause sinking of said entire particles below the surface of said fatty layer.

References Cited in the file of this patent UNITED STATES PATENTS 1,864,097 Sherman June 21, 1932 1,865,708 Sherman et a1. July 5, 1932 2,188,590 Bjorksten et al Ian. 30, 1940 2,202,254 Hyatt et al May 28, 1940 2,287,837 Srnyer June 30, 1942 2,348,128 Groak May 2, 1944 2,398,779 Dalton et a1 Apr. 23, 1946 2,611,313 Keller et al Sept.,23, 1952 2,618,573 Green Nov. 18, 1952 2,671,734 Rosenblum Mar. 9, 1954 2,729,575 Newman Jan. 3, 1956 2,744,031 Mumma May 1, 1956 2,752,271 Walkup et al. June 26, 1956 2,777,781 Kordig et a1. Jan. 15, 1957 

1. IN A METHOD OF PRODUCING A TRANSFER SHEET, THE STEPS OF FORMING ON ONE FACE OF A BACKING SHEET A SOLID LAYER OF A FATTY SUBSTANCE BEING SOLID AT ROOM TEMPERATURE AND BEING ADAPTED TO BE LIQUEFIED UPON BEING HEATED TO A PREDETERMINED ELEVATED TEMPERATURE; HEATING SAID FATTY LAYER AT SAID PREDETERMINED TEMPERATURE FOR A PERIOD OF TIME SUFFICIENT TO MELT AT LEAST THAT PORTION THEREOF WHICH IS FARTHEST DISTANT FROM SAID BACKING SHEET, DUSTING ONTO THE MOLTEN FREE FACE OF SAID FATTY LAYER A COVERING LAYER CONSISTING OF FINELY DIVIDED GRANULATED PULVERULENT SOLID MATERIAL WHICH IS INSOLUBLE IN SAID FATTY SUBSTANCE, SAID STEPS OF HEATING SAID FATTY LAYER AND OF APPLYING SAID PULVERULENT MATERIAL BEING CARRIED OUT IN SUCH A MANNER AS TO FATTY LAYER LEAVING PORTIONS OF SAID INDIVIDUAL PARTICLES EXPOSED AND EXTENDING OUTWARDLY OF THE FREE FACE OF SAID FATTY LAYER, AND ALLOWING THE THUS-FORMED COMPOSITE SHEET TO COOL SO AS TO SOLIDIFY SAID FATTY LAYER, THEREBY FIRMLY ADHERING SAID PARTIALLY EMBEDDED FINELY DIVIDED SOLID MATETERIAL TO THE OUTER PORTION OF SAID FATTY LAYER THUS FORMING A TRANSFER SHEET HAVING A PROTECTIVE, ROUGH OUTER PORTION FORMED OF THE OUTWARDLY EXTENDING FREE PORTIONS OF SAID PARTIALLY EMBEDDED PARTICLES. 